php - 如何从字符串中获取临时表结果？

Question

例如:
我的产品最佳排序字符串是“'8207,17631,16717,18545,9062,17469,17246,17750”

这个字符串是从 php 发布的，我不想将它们存储在数据库中。我想从 mysql 查询数据并左连接一个临时表，然后按临时表的排序进行排序。

如何从字符串中获取临时表？

我的代码看起来像下面这样:(错误的代码)

select
    p.products_id
from
    (
        select '18207,17631,16717,18545,9062,17469,17246,17750' as products_id
    ) as p
order by p.sort

Answer 1

您最好的方法可能是 - 使用 UNION 从字符串生成行集。然而，这将需要在您的应用程序中加入您的字符串，如下所示:

$string = '18207,17631,16717,18545,9062,17469,17246,17750';
$id     = 0;
$sql    = join(' UNION ALL '.PHP_EOL, array_map(function($item) use (&$id)
{
   return 'SELECT '.(++$id).' AS sort, "'.$item.'" AS products_id';
}, explode(',', $string)));

-最终结果将是这样的:

SELECT 1 AS sort, "18207" AS products_id UNION ALL 
SELECT 2 AS sort, "17631" AS products_id UNION ALL 
SELECT 3 AS sort, "16717" AS products_id UNION ALL 
SELECT 4 AS sort, "18545" AS products_id UNION ALL 
SELECT 5 AS sort, "9062" AS products_id UNION ALL 
SELECT 6 AS sort, "17469" AS products_id UNION ALL 
SELECT 7 AS sort, "17246" AS products_id UNION ALL 
SELECT 8 AS sort, "17750" AS products_id

但是，如果您想在 SQL 中执行此操作 - 这并不容易，因为 MySQL 不支持序列 - 因此，您需要使用一些技巧来生成所需的行集。有一种生成 N 连续数字的方法:

SELECT id+1
FROM 
  (SELECT
    (two_1.id + two_2.id + two_4.id + 
    two_8.id + two_16.id) AS id
   FROM
    (SELECT 0 AS id UNION ALL SELECT 1 AS id) AS two_1
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 2 id) AS two_2
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 4 id) AS two_4
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 8 id) AS two_8
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 16 id) AS two_16
   ) AS init
LIMIT 10

-这将导致 10 数字 1..10(检查 this fiddle)。使用它，您可以获得最终结果:

SELECT 
  ELT(id+1, 18207,17631,16717,18545,9062,17469,17246,17750) AS products_id,
  id+1 AS sort
FROM 
  (SELECT
    (two_1.id + two_2.id + two_4.id + 
    two_8.id + two_16.id) AS id
   FROM
    (SELECT 0 AS id UNION ALL SELECT 1 AS id) AS two_1
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 2 id) AS two_2
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 4 id) AS two_4
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 8 id) AS two_8
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 16 id) AS two_16
   ) AS init
HAVING 
  products_id IS NOT NULL

-检查this fiddle 。但是，这可能会很慢，我建议您使用您的应用程序层来构建所需的 SQL。